Method for producing a form-retaining roll of extensible tape



Nov. 6, 1962 D. w. SEAGER ETAL 3,061,886

METHOD FOR PRODUCING A FORM-RETAINING ROLL OF EXTENSIBLE TAPE Filed Aug. 12. 1960 FIG. 1

PRODUCTION OF WIDE TAPE INTERMEDIATE PRECONDITIONING OF WIDE TAPE INTERMEDIATE T0 INDUCE RELAXATION SIMULTANEOUS WINDING OF RELAXED TAPE INTERMEDIATE UNDER REGULATED TENSION AND AT PRESCRIBED TEMPERATURE FIG. 2 FIG. 3

INVENTORS DONALD W. SEAGER ALWYN B. PERRY BY 60, 5 smwk ATTORNEY.

United States Patent Ofifiee 3,061,886 Patented Nov. 6, 1962 7 3,061,886 METHOD FOR PRODUCING A FORM-RETAINING ROLL F EXTENlELE TAPE Donald William Seager, Winchester, and Alwyn Brooks Perry, Frankfort, Ky., assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Aug. 12, 1960, Ser. No. 4%,360 6 Claims. (Cl. 18-48) This invention relates to the manufacture and use of thin extensible tapes comprising a coating deposited upon one face of a plastic film and, more particularly, to such tapes made and used in the shape of form retaining rolls containing a long length of such tape.

Despite the large amount of study which has been devoted to the manufacture of such tapes whose coatings are provided for various functional reasons, such as printing, adhesive uses, magnetic purposes, protective uses, or ornamental purposes, practical problems arising from the inherent physical properties of the constituents of the tape, remains a cause of concern to both the manufacturer and the user. Such tapes are normally wound in roll form and are paid out from the roll during their intended use. A core member is provided for support of the wound tape and in order to store a maximum of tape in the roll, such core member preferably is of a relatively small diameter with respect to the overall diameter of the roll.

When the tape comprises an extensible film serving as a substrate for the functional coating, the wound roll often deforms when subjected to ambient temperatures encountered in storage, shipment, and use, due in large part to the forces exerted upon the film by the coating whose coefficients of expansion are different from those of the film. This deformation may result in axial telescoping or peripheral dishing of the roll of tape, wrinkling of the tape, loss of uniform wind of the tape, loosening of the tape upon its core, or other undesirable effects. To compensate for such deformation, various mechanical devices have been suggested such as special cores for supporting the tape, as, for example, resilient cores, large diameter cores, slotted cores, and the like. However, the compensating support given to the tape by the core is largely limited to the portion of the rolled tape contiguous the core itself, the unconfined sides of the roll becoming quite flexible, such flexibility increasing with decreasing ratio of the diameter of the core to the overall diameter of the roll. In contrast, the present invention has as a purpose the overcoming of the above-mentioned problems by suitable treatment of the tape itself, all to the end that the roll of tape may retain its specified form even under the ambient temperatures encountered after the roll is manufactured.

An object of the invention is to provide an improved form-retaining roll of extensible tape.

Another object is to provide a method for manufacturing an improved form-retaining roll of extensible tape.

These and other objects and advantages Will become apparent as the description proceeds and when considered in conjunction with the accompanying drawing in which:

FIG. 1 is a chart illustrating the sequence of steps en ployed in the production of the form-retaining rolls of tape characteristic of the invention;

FIG. 2 is a side elevation of a completed roll of tape; and

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2.

In accordance with the invention a thermoplastic thin film of substantial width has a functional coating applied thereto on one face thereof and this coated film serves as a tape intermediate article of manufacture. This intermediate is then suitably heated to cause a relaxing of the same with an accompanying physical sagging of the intermediate. The relaxed coated film is thereafter subjected to a winding tension and with the coated film being at a prescribed temperature during the winding of the same into roll form. Preferably, the wound tape is at this time deposited directly upon a central core and with the wide intermediate being subdivided into a plurality of firmly wound small rolls during such winding. However, the invention includes as alternatives the formation of a single wound roll of Wide width upon a Wide core as Well as the later rewinding and subdivision of the completely treated wide intermediate into separate small rolls. Each such roll has its tape convolutely wound on its core and with the parallel sides of the roll being rigid and unconfined, the innermost turn of the tape being supported by the core of the roll. Each roll as thus produced has the property of being substantially form-retaining when later subjected to temperatures within the range of 50 F. to 140 F. and which temperature range includes the ambient temperatures likely to be encountered by the roll during normal use of the tape.

The tape intermediate indicated in FIG. 1 comprises an extensible thermoplastic film having a functional coating on one face thereof, it being understood that the precise method of applying such coating in adhering relation to the film forms no part of the present invention and is conducted upon conventional apparatus by using conventional coating techniques. The precise type and thickness of the film and type and thickness of coating, moreover, are chosen in accordance with the intended usage of the finished tape. When, for example, the tape is to be employed for printing in typewriters, the film may comprise an extensible thermoplastic material, such as cellulose acetate, cellulose acetate butyrate, polyethylene, nylon, Mylar, or the like. The coating for such an illustrative tape may included a hot melt microcrystalline wax as a base material, a resinous base material, or the like. The film which jointly serves to support its adhering coating in a uniform layer and to give structural strength to the tape, preferably has the following combined characteristics: a modulus of elasticity in tension of not more than 4.0 10 p.s.i., an elongation of not less than 10%, a coefficient of linear thermal expansion greater than 7 X 10 per de ree centrigrade, and a thickness of not more than 2.0 mils. The lower limit of thickness of the film depends essentially upon the structural strength required of the tape during its use, it being apparent that When the requirement of structural strength is satisfied, the thinner the film the more of the tape which can be stored in a roll of given diameter.

The coating preferably has a thickness in all cases of not less than 0.05 mil and not more than 2.0 mils. As an example of a satisfactory commercial practice, the tape intermediate may be about inch in width and 0 feet long, being wound in temporary roll form upon passage from the apparatus in which the coating is applied to the film.

in carrying out the invention, the described large roll of tape intermediate is subjected to an essential preconditioning step wherein a relaxation of the coated film occurs with a concomitant physical sagging of the same. It has been found that the necessary relaxation will be induced when the coated film, depending upon the particular constituents of film and coating, is heated for a period of not less than 20 hours at a temperature of not less than 90 F. and not more than F. In general, for a given tape intermediate, the higher the preconditioning temperature, the shorter the preconditioning time required, provided at least 20 hours of treatment is secured. Greater lengths of time may, of course, be used with temperatures less than 140 F., but it has been found at the temperature of 90 F. no benefit is secured by periods of treatment in excess of 170 hours. A conventional oven or the like maintained at a constant temperature may be employed for this preconditioning. Following the preconditioning step, the relaxed tape intermediate may be stored indefinitely for later conversion, or may be promptly passed to the converting state of operation now to be described.

The conversion may be conducted upon any conventional winding apparatus capable of maintaining a prescribed tension upon the tape being wound and While that tape is at a prescribed temperature. As seen in FIGS. 2 and 3, the tape may be wound into small rolls each having a core -10 and with the wide tape intermediate preferably being slitted during the winding to form a plurality of such rolls simultaneously. Each roll has its innermost turn 11 of tape supported upon the periphery of the core, the two parallel sides 12 and 13 of the roll are unconfined and all portions of the outermost turn of the tape lie at a substantially uniform distance from the axis of the core. A leader strip 14 may also be attached to the trailing edge of the tape being wound upon the core and the diameter of the finished roll is at least twice the diameter of the core.

Surprisingly, it has been found that despite the essential preconditioning treatment, the tape also has to be at a prescribed temperature at the time of its winding in order to achieve the improved dimensional stability upon its roll, and which is characteristic of the invention. The reason for this phenomenon is not known but experience has shown that rolls of tape produced without the tape having been at the proper conversion temperature during its winding (all other steps of the process being followed) will not possess the dimensional stability found in rolls wherein such proper conversion temperature conditions were employed. This is all the more unexpected since the winding operation conducted upon the roll which, for example, may include about 925 feet of tape, may be accomplished in the order of 3 minutes and which time period may coincide with the period of conversion heating, as when the relaxed tape is at a temperature lower than the required conversion temperature upon being passed to the winding shaft. For the purpose of raising the temperature of the relaxed tape intermediate at the time of its winding, any suitably regulated heating means located adjacent the winding shaft of the winding apparatus may be employed. As in the case of the equipment used in the previously mentioned stages of operation, conventional winding and supplementary heating equipment forming no part of the present invention may also be employed at this conversion stage. It, therefore, is observed that, despite the brevity of time during which the tape under tension is required to be at the prescribed conversion temperature, rolls which have been processed under the correct conditions will possess a form-retaining stability during expansion and contraction occurring when they are later subjected to ambient temperatures ranging from about 50 F. to about 140 F.

These novel and useful results may be more fully appreciated when considered in conjunction with the following examples of the practice of the invention:

Example 1 A tape intermediate comprising a film of cellulose acetate butyrate with a thickness of 0.88 mil was provided with a transferable coating in the form of a petroleum wax base having a pigment dispersed therein for printing purposes in a typewriter, the coating having a thickness of 0.15 mil. The intermediate was preconditioned at a temperature of 100 F. for 24 hours. Thereafter, the relaxed tape intermediate was wound and subdivided into small rolls at a tension of 150 grams per lineal inch of its width and at a conversion temperature of 90 F. The finished rolls were of 7 inch width on a core of 1 /2 inch diameter and with an overall roll diameter of 4 inches. Upon being later subjected during use to ambient temperatures ranging from 50 F. to 140 F., the small rolls of tape remained dimensionally stable during their expansions and contractions without telescoping on their cores, becoming loose on such cores, or wrinkling. The innermost turn of each roll, moreover, remained firmly supported on its core and the unconfined sides of the roll remained rigid and parallel to each other when bending pressure was manually applied thereto transversely of the roll. In addition, no scalloping or dishing occurred at the periphery of the roll.

Example 1A The sametape intermediate described in Example 1 was preconditioned at a temperature of F. for 48 hours and thereafter the relaxed tape intermediate was wound into the small rolls at a tension of 100 grams per lineal inch of its width and at a conversion temperature of 90 F. The dimensional stability of the small rolls was substantially the same as the small rolls in Example 1.

Example 2 A tape intermediate comprising a film of 0.95 specific gravity polyethylene 0.75 mil in thickness was provided with a transferable coating in the form of a vegetable wax base having a pigment dispersed therein for printing purposes in a typewriter and with a coating thickness of 0.20 mil. The intermediate was preconditioned at a temperature of 100 F. for 36 hours. Thereafter, the relaxed tape intermediate was wound into small rolls at a tension of 300 grams per lineal inch of its width and at a conversion temperature of 105 F. The finished rolls exhibited the same dimensional stability found in the small rolls of Example 1.

Example 2A The same tape intermediate described in Example 2 was preconditioned at a temperature of 100 F. for 56 hours and thereafter the relaxed tape intermediate was wound into the small rolls at a tension of 150 grams per lineal inch of width and at a conversion temperature of F. The finished rolls exhibited the same dimensional stability found in the small rolls of Example 1.

Example 3 A tape intermediate comprising a film of 0.96 specific gravity polyethylene with a thickness of 0.90 mil was provided with a transferable coating in the form of a vegetable wax base having a pigment dispersed therein for printing purposes in a typewriter and with a coating thickness of 0.20 mil. The intermediate was preconditioned at a temperature of F. for 48 hours. Thereafter, the relaxed tape intermediate was wound into small rolls at a tension of 400 grams per lineal inch of its width and at a conversion temperature of F. The finished small rolls exhibited the same dimensional stability found in the small rolls of Example 1.

Example 3A The same tape intermediate described in Example 3 was preconditioned at a temperature of 100 F. for 60 hours and thereafter the relaxed tape intermediate was wound into the small rolls at a tension of 200 grams per lineal inch of its width and at a conversion temperature of 100 F. The finished rolls exhibited the same dimensional stability found in the small rolls of Example 1.

It will be understood that in carrying out the invention, tension applied to the relaxed tape during its winding is insuflicient to cause the film and its applied coating to become unduly attenuated, a residual extensibility at all times remaining in the film after it is wound upon the core.

Having thus described the invention with reference to preferred embodiments thereof, it will be apparent that various substitutions and changes in the materials employed may be made without departing from the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. The method of producing form-retaining rolls of extensible tape having substantial dimensional stability under ambient temperatures within the range of about 90 F. to 140 F, including, providing a wide tape intermediate comprising a thermoplastic film having a coating on one face thereof, heating said intermediate for a period of not less than 20 hours and at a temperature of not less than 90 F. to cause the same to relax and to assume a sag, and winding the relaxed intermediate under tension and at a predetermined temperature while under said tension thereby to form a roll of tape characterized by its dimensional stability under said ambient temperatures.

2. The method of claim 1 wherein said relaxed intermediate is subjected during said winding to a tension of not less than grams per inch of width of said intermediate and to a temperature of not less than 80 F. during said winding.

3. In the manufacture of a roll of extensible tape comprising a thermoplastic film having a coating on one face thereof, the steps comprising heating a sheet of said coated film at a temperature of not less than 90 F. nor more than 140 F. for a period of time not less than hours nor more than 170 hours and forming thereby a relaxed sheet of said coated film, and thereafter winding said relaxed sheet of said coated film under a tension of not less than 10 grams nor more than 400 grams per lineal inch of width of said relaxed sheet into a roll, said relaxed sheet being at a temperature of not less than 80 F. nor more than 140 F. during said winding under said tension.

4. In the manufacture of a roll of extensible tape comprising a film of cellulose acetate butyrate having a thickness of about 0.00088 inch with a coating of petroleum wax having a thickness of about 0.00015 inch on one face thereof, the steps comprising heating a sheet of said coated film at a temperature of about 100 F. for about 24 hours and forming a relaxed sheet of said coated film and thereafter winding said relaxed sheet of said coated film under a tension of about 150 grams per lineal inch of width of said relaxed sheet into a roll, said relaxed sheet being at a temperature of about F. during said Winding under said tension.

5. In the manufacture of a roll of extensible tape comprising a film of polyethylene having a thickness of about 0.00075 inch and a specific gravity of 0.95 with a coating of vegetable wax having a thickness of about 0.0002 inch on one face thereof, the steps comprising heating a sheet of said coated film at a temperature of about F. for about 36 hours and forming a relaxed sheet of said coated film and thereafter winding said relaxed sheet of said coated film under a tension of about 300 grams per lineal inch of Width of said relaxed sheet into a roll, said relaxed sheet being at a temperature of about F, during said winding under said tension.

6. In the manufacture of a roll of extensible tape comprising a film of polyethylene having a thickness of about 0.0009 inch and a specific gravity of 0.96 with a coating of vegetable wax having a thickness of about 0.0002 inch on one face thereof, the steps comprising heating a sheet of said coated film at a temperature of about 100 F. for about 48 hours and forming a relaxed sheet of said coated film and thereafter Winding said relaxed sheet of said coated film under a tension of about 400 grams per lineal inch of width of said relaxed sheet into a roll, said relaxed sheet being at a temperature of about 105 F. during said winding under said tension.

References Cited in the file of this patent UNITED STATES PATENTS 2,176,153 Semon Oct. 17, 1939 2,177,661 Kimble Oct. 31, 1939 2,451,597 Wheeler Oct. 19, 1948 2,772,774 Rabuse Dec. 4, 1956 2,779,684 Alles Jan. 29, 1957 2,812,550 Chavennes Nov. 12, 1957 2,876,893 Blackford et al. Mar. 10, 1959 2,903,379 Morland et al. Sept. 9, 1959 2,952,033 Goodwin Sept. 13, 1960 

1. THE METHOD OF PRODUCING FORM-RETAINING ROLLS OF EXTENSIBLE TAPE HAVING SUBSTANTIAL DEMENSIONAL STABILITY UNDER AMBIENT TEMPERATURES WITHIN THE RANGE OF ABOUT 90* F. TO 140*F. INCLUDING, PROVIDING A WIDE TAPE INTERMEDIATE COMPRISING A THERMOPLASTIC FILM HAVING A COATING ON ONE FACE THEREOF, HEATING SAID INTERMEDIATE FOR A PERIOD OF NOT LESS THAN 20 HOURS AND AT A TEMPERATURE OF NOT LESS THAN 90*F. TO CAUSE THE SAME TO RELAX AND TO ASSUME A SAG, AND WINDING THE RALAXED INTERMEDIATE UNDER TENSION AND AT A PREDETERMINED TEMPERATURE WHILE UNDER SAID TENSION THEREBY TO FORM A ROLL OF TAPE CHARACTERIZED BY ITS DIMENSIONAL STABILITY UNDER SAID AMBIENT TEMPERATURES. 